Charlie Hebdo killer brothers Said and Cherif Kouachi were shot after reportedly emerging from their bolt hole firing at police.
Minutes later armed officers stormed the Jewish supermarket in Paris where Amedy Coulibaly had been locked in a bloody stand off.
He had threatened to kill hostages if police acted against the Kouachis. Reports quoted police sources as saying four hostages were dead.
Ambulances streamed away from both scenes after the gunfire and explosions which brought the sieges to an end.
Hostages from the supermarket could be seen being led to safety. The Kouachis’ hostage was freed.
The operations finally brought to an end the worst spate of terror attacks in France since 1961, a murderous spree that has rocked the country.
On another day of extraordinary developments, Coulibaly, an associate of the Charlie Hebdo killers, launched a fresh strike at the Hyper Cacher kosher store in Porte de Vincennes in the east of the capital.
That came hours after the Kouachi brothers were cornered in Dammartin-en-Goele, a town around 25 miles (40km) north of Paris.
Two police officers were injured in the gun battle with the brothers.
Coulibaly, 32, was also behind the murder of a policewoman in the Paris suburb of Montrouge yesterday morning.
He is believed to have been connected to the Kouachis, who started the killing spree on Wednesday morning when they attacked the offices of satirical magazine Charlie Hebdo.
All three men were known to the French security authorities.
There were reports that four hostages were killed at the supermarket, which would take the death total since Wednesday to 20.
One of the supermarket hostages managed to call her daughter, who told Europe 1: “She called me and told me ‘I am in the shop, I love you’.”
The daughter added: “I am scared. Someone told me there have been two deaths. No one has told me if it is my mother or not.”
Hostage taker Coulibaly opened fire in the supermarket before telling police who flooded the area: “You know who I am.”
He then threatened to kill his captives if police launched an operation against the Kouachi brothers cornered on the industrial estate in Dammartin-en-Goele.
Police issued a photograph of Coulibaly and appealed for help tracking him down as part of the investigation into the “voluntary homicide” of the police woman in Montrouge.
Police also want to trace Hayat Boumeddiene, a 26-year-old woman said to have been Coulibaly’s partner.
It is understood that the Kouachi brothers, who were well-known for holding jihadist views, were on a British watch and no-fly list to prevent them from entering the UK or passing through a British airport.
US intelligence placed the brothers on the list at the same time as Britain.
But questions will now be asked about how closely the pair were monitored by the French authorities.
The BBC reported that a woman who was held hostage while shopping in the store had told a relative by phone that there were more than two people killed there - in fact she had said there were five people dead.
It was reported that security sources said four people were critically wounded after the supermarket siege.
Police officers were thought to be among those hurt, although their conditions were unclear.
The Kouachis stole a Peugeot earlier today in the town of Montagny Sainte Felicite, triggering a car chase during which gunfire was reported.
The enormous operation to apprehend the Kouachi brothers ended on its third day at the premises of a printing firm called Creation Tendance Decouverte on an industrial estate in Dammartin-en-Goele.
Before they were killed, they were said to have declared they want to die “as martyrs”.
A salesman told how he inadvertently shook the hand of one of the terrorists when he arrived for a meeting with the owner of the printing firm this morning, whose name he gave as Michel.
The eyewitness, named as Didier, told radio station France Info that he encountered a “heavily armed” man dressed in black and wearing a bullet-proof vest.
He said: “I encountered a terrorist and shook his hand. When I arrived, my customer came out with an armed man who looked like a police officer. My customer told me to leave.
“(The armed man) said to me ‘I am the police. Go, we do not kill civilians’.
“I decided to call the police. I guess that was one of the terrorists.”
He went on: “I did not formally recognise them. They were dressed like police. It could have been a police officer if he had not said to me ‘We do not kill civilians’.
“They were heavily armed. I was in front of the business, I shook Michel’s hand and the hand of one of the terrorists. After I left, Michel shut the gate behind me. I knew something was wrong. I have been very lucky this morning.”
A lockdown was imposed in the surrounding area as scores of heavily armed police surrounded the building.
Residents in the vicinity were warned to stay in their homes and children were being kept inside schools.
Speaking from a local high school, Marion Genay said she was one of 900 people being kept inside.
She told the BBC: “We are really scared. We all called our parents to know if they are OK or not. We have to wait in the high school.
“They say to us ‘stay in the high school and stay calm’ but we are really scared.”
Asked when she was first aware of the situation, she said: “Someone told me there are terrorists near my school.”
A woman named only as Anne was quoted by RTL as saying she feared for her daughter, who works in the industrial zone.
She said: “My daughter is still there and I want to stay here because I am scared for her.
“She called me this morning to tell me there had been shots.”
The Community Security Trust (CST), which provides security and training for Jewish communities in the UK and monitors anti-semitic incidents, said it has asked for increased police patrols in Jewish areas in London and Manchester over the weekend in the light of the Paris attack.
The charity said: “Although there is currently no known link to the UK we believe it is important for us to ensure that security across the Jewish community is at an appropriate level this Shabbat.”
French Interior Minister Bernard Cazeneuve told reporters: “The events show how great the challenge we are facing is, and the violence the terrorists are capable of.
“We have mobilised our forces, we have trained them, we have kept in touch with our partners in the European Union, to be more efficient in our fight against terrorism.”
He said colleagues from the EU and the US were invited to come to Paris on Sunday to draw conclusions from the recent events.
“We have a duty to be evolving to face this challenge, it is a serious problem.”
Mr Hollande told the nation: “I call you all to be vigilant, to remain united and remain mobilised. Vigilance is something the state must demonstrate.
“Make sure that we can live quietly without - at any time - being the object of the threat of a risk. However, we have to be vigilant.
“I ask you to remain united - it’s our best weapon. It shows we are determined to fight against anything that can divide us.
“We must not be divided.
“We must also mobilise to answer to these attacks, through force when we have to, but we must also do this through solidarity.
“Our ideas are bigger than us, we are capable of defending that value wherever it is threatened.
“Several leaders have let me know that they will be here for the big gathering that is taking place on Sunday. I will be with them, and I hope all the French people will stand on Sunday, to defend the values of democracy, freedom, pluralism, which we are so attached to, and Europe represents, which will come out even stronger.”